1. Field of the Invention
The invention relates, in general, to communication systems that include cognitive radios and/or software defined radios (SDRs) to achieve efficient and reliable spectrum use without harmful interference to incumbent services such as television (TV) receivers. More particularly, the invention relates to a method, and systems/devices configured to perform such a method, for controlling spectrum use by base stations and consumer premise equipment so as to allow unlicensed radios or other communication devices to operate in broadcast bands previously set aside for licensed users or services such as the TV broadcast bands. The method and related systems may be developed in some embodiments to comply with standards and protocols distributed by the Institute of Electrical and Electronics Engineers (IEEE) 802.22 Working Group.
2. Discussion of the Related Art
The IEEE formed the IEEE 802.22 Working Group to develop protocols for an interoperable air interface for use in spectrum allocated to TV broadcast service and to provide wireless services such as broadband access a point-to-multipoint wireless regional area network (WRAN).
The WRAN system is intended to provide packet-based transport capabilities in wireless broadband services such as internet access, data transport, streaming video, VoIP, and other services that are presently available to much of the population using digital subscriber (DSL) technologies or digital cable modems.
WRAN technology has been initially targeted at wireless broadband or remote access for users in geographically dispersed, sparsely populated areas. The use of TV broadcast bands or UHF bands as a license exempt spectrum for WRAN provides a non-line of sight transmission range of up to 100 kilometers but more typically 30 to 70 kilometers, which is significantly greater than ranges available with WiFi and wireless networks.
The target markets or users of the WRAN-based services are single family residential units, multi-dwelling units, small office/home office locations, small businesses, and remote public and private campuses. A WRAN system based on IEEE 802.22 protocols will likely make use, in a non-interfering manner, of unused TV broadcast channels, i.e., TV channels with bandwidths of 6, 7, and 8 MHz in a frequency range of 41 to 910 MHz (e.g., 54 to 862 MHz in the United States with a 6 MHz channel bandwidth).
An IEEE 802.22 system is generally a fixed point-to-multipoint wireless air interface in which the point is a base station (BS) that manages its own cell or coverage area and all associated consumer premise equipments (CPEs) or multipoints. Each CPE represents a user of the wireless services provided by the BS operator. During operations, the BS controls the access medium in its cell such as by setting the channel used for BS and CPE broadcasts to form the wireless link. The BS transmits in the downstream to the various CPEs, which respond back to the BS in the upstream direction, and these communications may be thought of as downlink and uplink communications or signals. The BS and CPE need to be designed to communicate without interfering with licensed or primary users. With this in mind, the BS manages spectrum or channel usage and uses sensing of existing channels to protect incumbent or primary users.
In some proposed WRAN, each BS operates on a single channel for an operation period, e.g., up to two seconds as presently indicated by IEEE 802.22 protocols, and then performs sensing during a quiet period, e.g., 20 to 100 milliseconds depending on sensing technology and mechanisms utilized by the BS and CPEs. If an incumbent or other use of the channel is sensed, the BS halts operations until the channel becomes available. A single channel WRAN is effective in protecting incumbent services, but halting operations or data transmissions during a quiet time results in underutilization of the channel to transmit digital data (e.g., in about every two second period there is up to 100 milliseconds without transmissions).
Hence, there remains a need for improved methods, and devices that implement such methods, for managing use and allocation of the radio spectrum in WRAN and other networks that communicate over channels in unused but licensed bands such as by using the TV bands of the radio spectrum.